Post on 29-Jan-2016
transcript
Requirements for good tissue Requirements for good tissue microarray (TMA) resultsmicroarray (TMA) results
Thick donor tissue blocks• At least 2 mm
• Best if > 3mm
Guide slide must represent the last section cut from the block
Selection of target tissue most likely to be present through full thickness of the block
“Tight” circling of targets required
Back to home page
Use of histologic sections that are not Use of histologic sections that are not representative of the cut surface of the representative of the cut surface of the block, and imprecise circling leads to block, and imprecise circling leads to the missing of target tissue, due to the the missing of target tissue, due to the “blind” nature of tissue core sampling “blind” nature of tissue core sampling
during the TMA manufacture.during the TMA manufacture.
Back to home page
Tissue architecture changes with Tissue architecture changes with depth of sectioningdepth of sectioning
Tumor with solid and cystic components: histologic sections taken from different levels of the Tumor with solid and cystic components: histologic sections taken from different levels of the block. Note in particular that the cystic areas and the edges of the solid tumor change in position block. Note in particular that the cystic areas and the edges of the solid tumor change in position within the tissue.within the tissue. Back to home page
Section of breast tissue: A heterogeneous population of adipose, fibrous and epithelial structures.
Back to home page
The desired target tissue: normal breast epithelium
Back to home page
Imprecise circling may lead the maker of the TMA to miss the target tissue.
Back to home page
Tighter circling of the area will result in a higher success rate in capturing target tissue.
Back to home page
In tissues with widely-dispersed target tissue, another strategy is to circle small areas for individual needle placement.
Back to home page
Some tissues will have target tissue that contains internal undesirable areas.
Back to home page
Tight circling may still result in non-target areas being sampledBack to home page
Fill in these areas to help guide the maker of the TMA.Back to home page
Problems inherent to tissueProblems inherent to tissue
Tissue targets smaller than the thickness of the block, and or small targets which do not maintain a vertical orientation will not be present in all sections of a TMA• Breast ducts and lobules are prime examples
Back to home page
Problems inherent to tissue:Problems inherent to tissue:small size of target tissue elementssmall size of target tissue elements
““Some well-differentiated cancers or other Some well-differentiated cancers or other smaller lesions, as well as normal glandular smaller lesions, as well as normal glandular tissues, retained their morphology for a few dozen tissues, retained their morphology for a few dozen sections”sections”
Olli Kallioniemi in Tissue microarrays for high-throughput molecular profiling of tumor specimens Nature Medicine 7:844, 1998
Back to home page
The ideal target tissue architecture is a cylinder, which is the full The ideal target tissue architecture is a cylinder, which is the full thickness of the paraffin block.thickness of the paraffin block.
Back to home page
This shape would ensure that target tissue is present in the This shape would ensure that target tissue is present in the sampled tissue core in every section of the tissue microarray.sampled tissue core in every section of the tissue microarray.
Back to home page
Unfortunately, many tissue elements change their location inUnfortunately, many tissue elements change their location inthe paraffin block and/or are not full thickness. This cannot the paraffin block and/or are not full thickness. This cannot be fully predicted from examination of the surface of the be fully predicted from examination of the surface of the block.block. Back to home page
To address this issue, it is wise to consider having more than To address this issue, it is wise to consider having more than one core per target tissue in the TMA, and to “double stack” one core per target tissue in the TMA, and to “double stack” the cores. This helps to ensure target tissue is present in more the cores. This helps to ensure target tissue is present in more sections of the TMA.sections of the TMA.
Back to home page
Approaches to dealing withApproaches to dealing with“difficult” tissue targets“difficult” tissue targets
Use more than one core to sample tissue
Use larger core sizes“Doublestack” cores
Back to home page
0.6mm
1.0mm
2.0mm
1.5 mm
TMA block, with tissue core diameters as indicatedTMA block, with tissue core diameters as indicated
Back to home page
TMA spot sizes:TMA spot sizes:microscopic imagesmicroscopic images
20 X original magnification20 X original magnification
Back to home page
Double stacking of TMA coresDouble stacking of TMA cores
Two cores are removed Two cores are removed from target tissue in from target tissue in the donor block.the donor block.
The cores are stacked, The cores are stacked, one on top of the other in one on top of the other in the recipient TMA block.the recipient TMA block.
Back to home page
TMA exampleTMA example
A TMA is to be constructed in 4 copies, with A TMA is to be constructed in 4 copies, with two core positions of target tissue per two core positions of target tissue per recipient TMA block, with each core recipient TMA block, with each core position to be double stacked.position to be double stacked.• Requires 16 donor coresRequires 16 donor cores• Uses approximately a “square” of donor target Uses approximately a “square” of donor target
tissue with 4 mm sidestissue with 4 mm sides
Back to home page
Donor tissue after TMA manufactureDonor tissue after TMA manufacture
16 cores
Back to home page